Rack Bush Groove Structure for Reduced Steering Time Lag
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Solution Overview
Problem
The existing rack bush in rack-and-pinion steering mechanisms experiences time lag in steering operation due to compressive deformation of elastic rings under reaction forces from tires, affecting the feeling of steering.
Innovation Solution
A bearing design with a bush body and elastic rings, featuring mounting grooves with large-diameter and small-diameter parts, where the elastic ring is positioned to face the reaction force, reducing the gap between the bush body and housing, thereby improving rigidity and reducing time lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the elastic rings are mounted on the bearing body and abutted against the inner peripheral surface of the housing, then the rack bar is tightened and clearance is eliminated, but the elastic rings are compressively deformed under reaction force causing time lag in steering operation
Solution Approach 1:
The mounting groove is designed with different radial depths at different circumferential positions, creating local quality variations. The groove bottom has a first radius at the reaction force supporting surface side and a second radius at the opposite side, allowing the elastic ring to be mounted at different depths to optimize both tightening and response characteristics.
Solution Approach 2:
The invention changes the geometric parameters of the mounting groove, specifically the radial depth varying in the circumferential direction. By adjusting the first and second radii of the groove bottom, the mounting depth of the elastic ring is optimized to balance the tightening effect against the time lag caused by compressive deformation.
2Strength
If the elastic rings are positioned to face the reaction force supporting surface, then rigidity against reaction force is improved, but the compressive deformation of elastic rings increases
Solution Approach 1:
The mounting groove provides local quality variation by having different radial depths at different circumferential positions. At the reaction force supporting surface side, the groove allows optimal positioning of the elastic ring to maximize rigidity, while at other positions, the groove depth is adjusted to reduce compressive deformation and time lag.
Solution Approach 2:
The elastic ring is mounted at different depths at different circumferential positions rather than uniformly. This partial differentiation allows the elastic ring to provide maximum support where needed (at the reaction force supporting surface) while minimizing deformation and time lag at other positions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The improved design enhances rigidity against tire reaction forces, reduces movement of the rack bar, and minimizes the impact on steering operation feel without compromising sliding characteristics.
Implementation Method 1
the elastic ring is mounted on the bush body; the bush body has a mounting groove formed in an outer peripheral surface in a circumferential direction for mounting the elastic ring
Implementation Method 2
the elastic rings are compressively deformed and moved within the housing owing to the reaction force from the tires inputted into the rack bar
Data Source
Figure 1
Figure 2(A)~2(C)
Figure 3(A)~3(E)
AI summary
To reduce the effect of a steering operation on feeling. A rack bush (1) comprises: a bush body (2) that is accommodated in a cylindrical housing (4), supports a load exerted on a rack bar (5) while allowing the rack bar (5) to move in the direction of an axial center O, and can be extended and retracted in a radial direction; and an elastic ring (3) mounted on the bush body (2). The bush body (2) has a mounting groove (28) for mounting the elastic ring (3), the mounting groove (28) being formed peripherally in an outer peripheral surface (22), and the mounting groove (28) having a large-diameter part (280) where the circumferential radius of a groove bottom (28) is a first radius r1, and a small-diameter part (281) where said radius is a second radius r2 that is less than the first radius r1. This configuration allows the formation of an elastic ring protruding part (10), in which the elastic ring (3) protrudes greatly from the outer peripheral surface (22) of the bush body (2), and an elastic ring embedded part (11), in which the elastic ring (3) is embedded in the outer peripheral surface (22) of the bush body (2).